External and internal conditions necessary for or associated with sperm capacitation and the acrosome reaction in mammals are analyzed. Membrane-bound phosphatase which is very likely responsible or associated with the acrosome reaction will be investigated by biochemical and cytochemical techniques. Possible changes in globular (protein) particles in the sperm membranes during capacitation and acrosome reaction of spermatozoa are studied using freeze-fracture technique. The mechanisms of sperm-egg fusion will be investigated utilizing various reagents including local anesthesia.